Machines such as, for example, off-highway haul trucks, motor graders, snow plows, and other types of heavy equipment are used to perform a variety of tasks. Some of these tasks involve carrying or pushing large, awkward, loose, and/or heavy loads up steep inclines or along rough or poorly marked haul roads. And, because of the size and momentum of the machines and/or because of poor visibility, these tasks can be difficult for a human operator to complete effectively.
To help guide the machines safely and efficiently along the haul roads, some machines are equipped with sensors, for example, RADAR sensors, SONAR sensors, LIDAR sensors, IR and non-IR cameras, and other similar sensors. These sensors are often connected to a visual display and/or a guidance system of the machine such that control over machine maneuvering may be enhanced or even automated. In order for these display and guidance systems to operate properly, the information provided by the sensors must be accurate. And, even though most machine sensor systems are calibrated when first commissioned, vibrations, collisions, and damage to the machine during operation can reduce the quality of information provided by the sensors. As such, periodic recalibration through the use of an on-site calibration object can be beneficial.
An exemplary on-site calibration object is described in U.S. Patent Publication No. 2006/0164295 (the '295 publication) by Focke et al. published on Jul. 27, 2006. Specifically, the '295 publication describes a system for simultaneous calibration of two different types of sensors, for example an image sensor and a radar sensor mounted on a motor vehicle. During calibration of the two sensors, the motor vehicle is aligned in front of a calibration object in such a way that the image and radar sensors detect reference features of the calibration object. The calibration object is a flat or three-dimensional object of between ten and fifty features having particular properties such as a high contrast, a reflective surface, or a particular shape, the features being connected to each other by a mechanical mounting device. After the motor vehicle is aligned in front of the calibration object, the features are detected by the sensors and calibration data is determined by each sensor. The calibration data is stored, analyzed, displayed, transmitted, and further processed by a downstream system. In addition, the calibration data is further used directly for calibration of the participating sensors. For example, the calibration data is used for automatic correction of a deviation of a sensor axis in relation to a vehicle longitudinal axis or by an automotive technician for mechanical adjustment of sensor placement. These procedures are possible during manufacture or repair of the motor vehicle.
Although the sensor system of the '295 publication may be helpful in recalibrating machine-mounted sensors, the benefit may be limited. That is, for optimum accuracy, the machine of the '295 publication must be precisely aligned relative to the calibration object, which can be difficult to do in a worksite setting. Any error in this alignment may result in an accuracy reduction of the sensed information. In addition, the mechanical adjustment of the sensor location on the motor vehicle may be time consuming and expensive, and be required more often than when the vehicle is undergoing scheduled repairs. Further, the automated calibration described in the '295 patent (i.e., about only the sensor axis) may be limited. In addition, taking the vehicle out of commission to accomplish the required repairs and calibration may reduce a productivity and efficiency of the vehicle.
The disclosed sensor calibration system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.